The environmental scientists have uncovered a serious problem for which there is no prior warning. Our knowledge of the workings of the atmosphere has been appealingly poor, and one consequence of that lack of understanding is the strong possibility that ultra-violet (UV) radiation will increase in intensity throughout the earth.
Radiation from the sun includes UV radiation, along with the visible light. On penetrating the atmosphere and being absorbed by biological tissues, UV radiation damages protein and DNA molecules at the surface of all living things. This occurs in sunburn. If the entire amount of UV radiation falling on the stratosphere reached the earth’s surface, it is fearful that any life would be able to survive. The more damaging effects of the UV rays is mostly avoided because most of the UV radiation over 99 % is absorbed by ozone in the upper stratosphere. For this reason, stratospheric ozone is commonly referred to us the Ozone shield or the Ozone Layer.
In the autumn of 1985, some British atmospheric scientists working in Antarctica reported a gaping ‘hole’ (actually, a thinning of one area) in the stratospheric ozone layer of the South Pole. There is an area equal to the size of the United States, where ozone levels were 50% lower than normal. Scientists had assumed that the loss of Ozone, if it occurred would be slow, gradual and uniform over the whole planet. The ’hole’ came as a surprise and if it had occurred anywhere but over the South Pole, the UV damage would have been extensive.
News of the ozone ‘hole’ stimulated an enormous research effort. A unique set of conditions were found to be responsible for the ozone hole. In summer, gases such as nitrogen oxide and Methane react with Chlorine Monoxide and Chlorine to trap the chlorine forming so-called chlorine reservoirs, preventing much ozone depletion.
High above the earth is the stratosphere where a small number of ozone molecules shield all life from harmful ultraviolet radiation. Ozone, an unstable form of oxygen containing 3 oxygen atoms(O3), fall apart into an oxygen atom(O) and an oxygen molecule(O2) when it absorbs UV radiation. However a fresh supply of ozone forms continually in the stratosphere, producing a delicate chemical balance in which a layer of less than 4.5 trillion kilograms of ozone, about 3 or 4 ozone molecules for every million molecule of air, blanket the planet. The balance is threatened by chemicals called chlorofluorocarbons or CFCs, such as the Fluoro Carbon-11. There, they decompose and release chlorine atoms, which cause ozone to break down. The difference is that each chlorine atom destroys as many as 100,000 ozone molecules faster than nature can replenish them. As a result, the ozone layer is thinning, forming a hole that lets damaging UV radiations reach the Earth. The depletion of ozone layer, allows more UV radiation to reach the earth which affects the humans, the increased UV radiation increases the incidence of cataract, skin cancer and decline in the functioning of the Immune system.